program mynormal6
	version 9.1
	if replay() {
		if (`"`e(cmd)'"' != "mynormal6") error 301
		Replay `0'
	}
	else	Estimate `0'
end

program Estimate, eclass sortpreserve
	syntax varlist [if] [in]		///
		[fweight pweight] [,		///
		noLOg				/// -ml model- options
		noCONStant			///
		CLuster(varname)		///
		HETero(varlist)			///
		noLRTEST			/// <- NEW
		Level(cilevel)			/// -Replay- option
		*				/// -mlopts- options
	]

	// check syntax
	mlopts mlopts, `options'
	local cns `s(constraints)'			// <- NEW
	gettoken lhs rhs : varlist
	if "`cluster'" != "" {
		local clopt cluster(`cluster')
	}
	if "`weight'" != "" {
		local wgt "[`weight'`exp']"
	}
	if "`log'" != "" {
		local qui quietly
	}
	// mark the estimation sample
	marksample touse
	markout `touse' `hetero'
	markout `touse' `cluster', strok

	if "`constant'" == "" {				// NEW block
		`qui' di as txt _n "Fitting constant-only model:"
		ml model lf mynormal_lf				///
			(mu: `lhs' = )				///
			(lnsigma: `hetero')			///
			`wgt' if `touse',			///
			`log'					///
			`mlopts'				///
			nocnsnotes				///
			missing					///
			maximize
		if "`lrtest'" == "" {
			local contin continue search(off)
		}
		else {
			tempname b0
			mat `b0' = e(b)
			local contin init(`b0') search(off)
		}
		`qui' di as txt _n "Fitting full model:"
	}

	// fit the full model
	ml model d2 mynormal_d2				///
		(mu: `lhs' = `rhs', `constant')		///
		(lnsigma: `hetero')			///
		`wgt' if `touse',			///
		`log'					///
		`mlopts'				///
		`clopt'					///
		`contin'				/// <- NEW
		missing					///
		maximize

	ereturn local cmd mynormal6

	Replay , level(`level')
end

program Replay
	syntax [, Level(cilevel) ]
	ml display , level(`level')
end
